Method for depositing a semiconductor structure on a surface of a substrate and related semiconductor structures

ABSTRACT

A method for depositing a semiconductor structure on a surface of a substrate is disclosed. The method may include: depositing a first group IVA semiconductor layer over a surface of the substrate; contacting an exposed surface of the first group IVA semiconductor layer with a first gas comprising a first chloride gas; and depositing a second group IVA semiconductor layer over a surface of the first group IVA semiconductor layer. Related semiconductor structures are also disclosed.

FIELD OF INVENTION

The present disclosure generally relates to methods for depositing a semiconductor structure on a surface of a substrate and particularly methods for depositing a semiconductor structure including group IVA semiconductor layers with thin interface layers. The present disclosure also generally relates to semiconductor structures and particularly semiconductor structures including adjacent group IVA semiconductor layers with thin interface layers.

BACKGROUND OF THE DISCLOSURE

The down scaling of semiconductor device structures, such as, for example, complementary metal-oxide-semiconductor (CMOS) devices, has led to significant improvements in speed and density of integrated circuits. However, conventional device scaling faces immense challenges for future technology nodes.

As the down scaling of semiconductor devices continues and semiconductor device layers become increasing thinner, the interface layer, also referred to as the interface region disposed between two adjacent semiconductor layers, may become increasingly significant, both in terms of semiconductor device fabrication/integration as well as in semiconductor device performance. For example, a key feature in next generation semiconductor devices comprising nanowire structures is the compositional abruptness of the interface between adjacent semiconductor layers of differing composition. Accordingly, methods are desirable for controlling the interface layer disposed between two semiconductor layers of differing compositions as well as semiconductor structures including interface layers with desirable characteristics.

SUMMARY OF THE DISCLOSURE

In accordance with at least one embodiment of the disclosure, a method for depositing a semiconductor structure on a surface of a substrate is disclosed. The method may comprise: depositing a first group IVA semiconductor layer over a surface of the substrate; contacting an exposed surface of the first group IVA semiconductor layer with a first gas comprising a first chloride gas; and depositing a second group IVA semiconductor layer over a surface of the first group IVA semiconductor layer.

The embodiments of the disclosure may also provide semiconductor structures comprising: a silicon substrate; a first silicon germanium (Si_(1-x)Ge_(x)) layer disposed over a surface of the silicon substrate; a first silicon layer disposed over the first silicon germanium (Si_(1-x)Ge_(x)) layer; and a first interface layer disposed directly between the first silicon germanium (Si_(1-x)Ge_(x)) layer and the first silicon layer; wherein the interface layer has a thickness of less than 15 Angstroms.

For the purpose of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments having reference to the attached figures, the invention not being limited to any particular embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the invention, the advantages of embodiments of the disclosure may be more readily ascertained from the description of certain examples of the embodiments of the disclosure when read in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates a cross sectional transmission electron microscope image of a semiconductor structure deposited by prior art methods;

FIG. 2 illustrates a process flow diagram illustrating an exemplary method in accordance with the embodiments of the disclosure;

FIGS. 3A-3E illustrate cross sectional schematic diagrams of semiconductor structures formed during an exemplary process flow in accordance with the embodiments of the disclosure;

FIG. 4 illustrates a cross sectional transmission electron microscope image of a semiconductor structure deposited according to the embodiment of the disclosure.

It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below.

As used herein, the term “substrate” may refer to any underlying material or materials that may be used, or upon which, a device, a circuit or a film may be formed.

As used herein, the term “silicon germanium” and “Si_(1-x)Ge_(x)” may refer to an alloy of silicon and germanium, wherein the ratio of germanium to silicon may range as 1≥(x)>0.

As used herein, the term “chemical vapor deposition” may refer to any process wherein a substrate is exposed to one or more volatile precursors, which react and/or decompose on a substrate surface to produce a desired deposition.

As used herein, the term “group IVA semiconductor” may refer to a semiconductor material comprising at least one member of group IVA of the periodic table, including but not limited to, carbon (C), silicon (Si), germanium (Ge), and tin (Sn). The term “group IVA semiconductor” may also refer to alloys of carbon (C), silicon (Si), germanium (Ge), and tin (Sn), including, but not limited to, SiGe, SiC, SiGeSn, and GeSn, as well the group IVA semiconductors and group IVA semiconductor alloys including one or more dopant species.

As used herein, the term “chloride gas” may refer to a gaseous reactant which comprises a chlorine (Cl) component.

As used herein, the term “gas” or “gaseous reactant” may refer to a single gaseous reactant or a gaseous mixture composed of multiple gaseous reactants.

As used herein, the term “group IVA gas” may to refer to a gaseous reactant which comprises a component from group IVA of the periodic table, including, but not limited to carbon (C), silicon (Si), germanium (Ge), and tin (Sn).

As used herein, the terms “interface thickness” and “interface region” may refer to the thickness of the region between two adjacent semiconductor layers and particular the interface thickness of the interface region between two adjacent semiconductor layers comprising differing compositions. For example, the interface thickness between a silicon (Si) layer and an adjacent silicon germanium (Si_(1-x)Ge_(x)) layer, wherein (x)=0.30, may be defined as the thickness of the region disposed between the two adjacent semiconductor layers wherein the composition of the interface region does not comprise that of silicon (Si) or that of (Si_(1-x)Ge_(x)) wherein x=0.030, but rather is a composite of the two adjoining semiconductor compositions, since the interface between the two adjoining semiconductor materials may not be atomically abrupt. As described herein in relation to the embodiments of the disclosure, the interface thickness between two adjacent semiconductor layers of differing composition may be determined utilizing a number of analytic methods, including, but not limited to, spectroscopic ellipsometry (SE), secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and x-ray reflectometry (XRR). It should also be noted that the “interface thickness” as referred to herein corresponds to the interface thickness between two adjoining “deposited” semiconductor layers and particular between two adjoining semiconductor layers deposited by a chemical vapor deposition process. As used herein, the term “interface thickness” does not refer to the interface thickness between two adjoining semiconductors formed by a bonding process.

In the specification, it will be understood that the term “on” or “over” may be used to describe a relative location relationship. Another element or layer may be directly on the mentioned layer, or another layer (an intermediate layer) or element may be intervened therebetween, or a layer may be disposed on a mentioned layer but not completely cover a surface of the mentioned layer. Therefore, unless the term “directly” is separately used, the term “on” or “over” will be construed to be a relative concept. Similarly to this, it will be understood the term “under”, “underlying”, or “below” will be construed to be relative concepts.

The embodiments of the disclosure may include methods for depositing a semiconductor structure on a surface of a substrate and particularly methods for depositing two or more adjacent group IVA semiconductors with thin interface layers. For example, the embodiments of the disclosure may be utilized to deposit a silicon (Si) layer over a surface of a silicon germanium (Si_(1-x)Ge_(x)) semiconductor layer with an intermediate interface region with a minimized thickness.

In some semiconductor device fabrication processes it may be necessary to deposit a plurality of semiconductor layers, of differing compositions, thereby forming a semiconductor layer stack comprising, a plurality of interface layers disposed between the adjoining semiconductor layers. For example, a semiconductor device comprising a “gate-all-around” semiconductor structure may comprise, a semiconductor layer stack including alternating layers of silicon germanium (Si_(1-x)Ge_(x)) and silicon (Si), such as, for example, a semiconductor layer stack comprising Si/(Si_(1-x)Ge_(x))/Si/(Si_(1-x)Ge_(x))/Si/(Si_(1-x)Ge_(x))/Si. In addition to “gate-all-around” semiconductor devices, certain semiconductor device structures may comprise quantum well regions, wherein a first semiconductor layer comprises a thin, e.g., nanometer scale, quantum well region, surrounded by a second semiconductor layer comprising a barrier material. In such semiconductor device applications, comprising thin, alternating semiconductor layers of differing compositions, the thickness of the interface region may be critical both in terms of the semiconductor fabrication/integration processes, as well as in the quality of the semiconductor device performance.

Not to be bound any particular theory, but it is believed that in prior art methods for depositing semiconductor layer stacks, comprising semiconductor materials of differing compositions, that when transitioning from a first semiconductor layer to the next adjoining second semiconductor layer that some atoms may have a tendency to segregate at the surface of the first semiconductor layer, and even form cluster defects, at the surface of the first semiconductor layer resulting in a “blurred”, non-abrupt interface between the two adjoining semiconductor layers. For example, FIG. 1 illustrates a cross sectional transmission electron microscope (TEM) image of a semiconductor structure 100, wherein the semiconductor structure 100 comprises a silicon substrate 102, a silicon germanium (Si_(1-x)Ge_(x)) layer 104 disposed directly on the silicon substrate 102, and an additional silicon (Si) layer 106 disposed over the silicon germanium (Si_(1-x)Ge_(x)) layer 104. In addition to the three semiconductor layers making up the semiconductor structure 100, disposed between the semiconductor layers are two interface layers 108 and 110. Interface layer 108 is disposed between the silicon substrate and the silicon germanium (Si_(1-x)Ge_(x)) layer 104, whereas interface layer 110 is disposed between the silicon germanium (Si_(1-x)Ge_(x)) layer 104 and the overlying additional silicon (Si) layer 106. Examination of the two interfaces layers 108 and 110 reveals that the interface layer 108 is considerably sharper, i.e., more abrupt or thinner, than the interface layer 110, wherein the interface layer 110 has significant thickness, resulting in a “blurred”, non-abrupt interface. The non-abrupt interface layer 110 between the silicon germanium (Si_(1-x)Ge_(x)) layer 104 and the overlying silicon (Si) layer may result from the segregation and/or clustering of atoms at the upper exposed surface of the silicon germanium (Si_(1-x)Ge_(x)) layer 104 during the deposition of the overlying silicon (Si) layer 106.

Methods and semiconductor structures are therefore desirable to deposit semiconductor structures with sharp, thin interface regions to enable more efficient device fabrication processes and higher performance semiconductor devices.

The embodiments of the disclosure may therefore include methods for depositing a semiconductor structure, the methods may comprise: depositing a first group IVA semiconductor layer over of a surface of a substrate; contacting an exposed surface of the first group IVA semiconductor layer with a first gas comprising a first chloride gas; and depositing a second group IVA semiconductor layer over a surface of the first group IVA semiconductor layer.

The methods of the disclosure are described in greater detail with reference to FIG. 2 which comprises a process flow diagram illustrating an exemplary method 200 and with reference to FIGS. 3A-3E which illustrate cross sectional schematic diagrams of semiconductor structures formed as part of the process flow of exemplary method 200.

The method 200 may commence with a process block 210 comprising, depositing a first group IVA semiconductor layer over a surface of a substrate. In more detail, the process may comprise providing a substrate, such as substrate 302 of FIG. 3A. In some embodiments of the disclosure, the substrate 302 may comprise a planar substrate (as illustrated in FIG. 3A) or a patterned substrate. The substrate 302 may comprise one or more materials including, but not limited to, silicon (Si), germanium (Ge), germanium tin (GeSn), silicon germanium (SiGe), silicon germanium tin (SiGeSn), silicon carbide (SiC), or a group III-V semiconductor material, such as, for example, gallium arsenide (GaAs), gallium phosphide (GaP), or gallium nitride (GaN). In some embodiments of the disclosure, the substrate 302 may comprise an engineered substrate wherein a surface semiconductor layer is disposed over a bulk support with an intervening buried oxide (BOX) disposed there between.

Patterned substrates may comprise substrates that may include semiconductor device structures formed into or onto a surface of the substrate, for example, the patterned substrates may comprise partially fabricated semiconductor device structures, such as, for example, transistors and/or memory elements. In some embodiments, the substrate may contain monocrystalline surfaces and/or one or more secondary surfaces that may comprise a non-monocrystalline surface, such as a polycrystalline surface and/or an amorphous surface. Monocrystalline surfaces may comprise, for example, one or more of silicon (Si), silicon germanium (SiGe), germanium tin (GeSn), or germanium (Ge). Polycrystalline or amorphous surfaces may include dielectric materials, such as oxides, oxynitrides or nitrides, such as, for example, silicon oxides and silicon nitrides.

In some embodiments of the disclosure, depositing a first group IVA semiconductor layer over a surface of a substrate may comprise, providing a silicon substrate including an exposed silicon growth surface and depositing the first group IVA semiconductor layer over the silicon surface of the substrate by a chemical vapor deposition process. For example, the substrate 302 of FIG. 3A, may be provided into a reaction chamber and the substrate may be heated to a deposition temperature within the reaction chamber. As a non-limiting example, the reaction chamber may comprise a reaction chamber of a chemical vapor deposition system. Embodiments of the present disclosure may include deposition processes that may be performed in a chemical vapor deposition system available from ASM International N.V. under the name Intrepid™ XP or Epsilon®. However, it is also contemplated that other reaction chambers and alternative chemical vapor deposition systems from other manufacturers may also be utilized to perform the embodiments of the present disclosure.

In some embodiments of the disclosure, the substrate 302 may be heated to a desired substrate temperature within the reaction chamber of the chemical vapor deposition system. In some embodiments, depositing the first group IVA semiconductor over a surface the substrate 302 may comprise, heating the substrate to a temperature of less than approximately 700° C., or less than approximately 600° C., or less than approximately 550° C., or less than approximately 500° C., or less than approximately 400° C., or even less than approximately 300° C.

In addition to controlling the substrate temperature during the deposition process, it may be desirable to also control the pressure within the reaction chamber to a desired set point. For example, the pressure within the reaction chamber during the deposition of the first group IVA semiconductor layer may be less than 760 Torr, or less than 100 Torr, or even less than 20 Torr.

In some embodiments of the disclosure, once the substrate has been heated to a desired deposition temperature and the pressure in the reaction chamber has been set, one or more precursor gases may be introduced into the reaction chamber and contact the substrate 302 thereby depositing the first group IVA semiconductor layer over a surface of the substrate 302 via a chemical vapor deposition process, as illustrated by the first group IVA semiconductor layer 304A in FIG. 3B. In some embodiments, the first group IVA semiconductor layer 304A may comprise at least one of silicon (Si), germanium (Ge), silicon germanium (Si_(1-x)Ge_(x)), germanium tin (GeSn), silicon carbide (SiC), or silicon germanium tin (SiGeSn).

In a particular embodiment of the disclosure, the first group IVA semiconductor layer 304A may comprise a silicon germanium (Si_(1-x)Ge_(x)) semiconductor layer, wherein the germanium composition (x) in the silicon germanium (Si_(1-x)Ge_(x)) semiconductor layer may comprise (x) less than approximately 1, or (x) less than approximately 0.8, or (x) less than approximately 0.6, or (x) less than approximately 0.5, or (x) less than approximately 0.4, or (x) less than approximately 0.3, or (x) less than approximately 0.2, or even (x) less than approximately 0.1. In some embodiments of the disclosure, depositing a first group IVA semiconductor layer 304A over a surface of the substrate 302 comprises, depositing a silicon germanium (Si_(1-x)Ge_(x)) layer with a germanium composition (x) of approximately 0.30.

In some embodiments, one or more precursor gases may be introduced into the reaction chamber in order to deposit the first group IVA semiconductor layer 304A. In some embodiments, the first group IVA semiconductor layer may comprise a silicon germanium (Si_(1-x)Ge_(x)) layer and the one or more precursor gases may comprise one or more silicon precursor gases and one or more germanium precursor gases.

In some embodiments of the disclosure, the one or more silicon precursor gases may comprise at least one of silane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀), isopentasilane (Si₅H₁₂), or neopentasilane (Si₅H₁₂). In some embodiments, the silicon source may comprise a higher order silane precursor with the general empirical formula Si_(x)H_((2x+2)). In some embodiments, the silicon precursor gas may comprise dichlorosilane (DCS). In some embodiments, the flow rate of the silicon precursor may be greater than 10 sccm, or greater than 50 sccm, or greater than 100 sccm, or ever greater than 200 sccm.

In some embodiments of the disclosure, the one or more germanium precursor gases may comprise at least one of germane (GeH₄), digermane (Ge₂H₆), trigermane (Ge₃H₈), or germylsilane (GeH₆Si). In some embodiments, the germanium precursor may comprise a Si—Ge-hydride precursor, such as, (H₃Ge)_(x)SiH_(4-x), wherein x=1-4, or (H₃Si)_(x)GeH_(4-x), where x−1-4. In some embodiments, the flow rate of the germanium precursor may be greater than 10 sccm, or greater than 50 sccm, or greater than 100 sccm, or ever greater than 200 sccm.

In some embodiment of the disclosure, the first group IVA semiconductor layer 304A may be deposited to a thickness of less than 500 nanometers, or less than 250 nanometers, or less than 100 nanometers, or less than 50 nanometers, or less than 25 nanometers, or less than 10 nanometers, or less than 5 nanometers, or even less than 1 nanometer.

Once the first group IVA semiconductor layer 304A has been deposited to a desired thickness, the exposed surface of the first group IVA semiconductor layer 304A may be subjected to a treatment process in order to minimize the interface region thickness between the first group IVA semiconductor layer 304A and a subsequent second group IVA semiconductor layer. Therefore, in some embodiments of the disclosure, the method 200 may continue with a process block 220 comprising, contacting an exposed surface of the first group IVA semiconductor layer with a first gas comprising a first chloride gas. For example, in some embodiments, the first chloride gas may comprise at least one of hydrochloric acid (HCl), or chlorine (Cl₂). In some embodiments of the disclosure, the first gas may further comprise a first group IVA gas. For example, in some embodiments, the first group IVA gas may comprise at least one of dichlorosilane, dichlorodisilane, trichlorosilane, tetrachlorosilane, hexachlorosilane, silane, or germane.

In some embodiments of the disclosure, the first chloride gas may be introduced into the reaction chamber at a flow rate of less than 400 sccm, or less than 200 sccm, or less than 100 sccm, or less than 50 sccm, or less than 25 sccm, or even less than 10 sccm. In some embodiments, the first group IVA gas may be introduced into the reaction chamber at a flow rate of less than 200 sccm, or less than 100 sccm, or less than 50 sccm, or less than 25 sccm, or even less than 10 sccm.

In particular embodiments of the disclosure, wherein the first gas comprises a first chloride gas and a first group IVA gas, the flow rate ratio of the first chloride gas in relation to the first group IVA gas may be regulated during the treatment process of the exposed surface of the first group IVA semiconductor layer 304A. For example, in some embodiments, the flow rate ratio of the first chloride gas in relation to the first group IVA gas may be regulated such that no net deposition, or substantially no net deposition, of material occurs on the exposed surface of the first group IVA semiconductor layer 304A. Not to be bound by any particular theory, but it is believed the first gas comprising a first chloride gas and a first group IVA gas may both passivate and etch the surface of the first group IVA semiconductor layer 304A thereby preventing, or substantially preventing, segregation and/or clustering of atoms at the surface of the first group IVA semiconductor layer 304A. Therefore, in some embodiments of the disclosure, the flow rate ratio of the first chloride gas to the first group IVA gas may be 10:1, or 5:1, or 2:1, or 1:1, or even 0.5:1. For example, in some embodiments of the disclosure, the first chloride gas may comprise hydrochloric acid (HCl) and the first group IVA gas may comprise dichlorosilane and the flow rate ratio of the hydrochloric acid (HCl) in relation to the first group IVA gas may be 2:1.

In some embodiments of the disclosure, the exposed surface of the first group IVA semiconductor layer 304A may be contacted with the first gas for a time period of less than 90 seconds, or less than 30, or even less than 10 seconds. In some embodiments, whilst contacting the first group IVA semiconductor layer 304A with the first gas, the substrate may be maintained at a desired temperature. For example, when contacting the substrate with the first gas, the substrate temperature may be maintained at a substrate temperature of less than approximately 700° C., or less than approximately 600° C., or less than approximately 500° C., or less than approximately 400° C., or less than approximately 300° C., or even less than approximately 200° C. In some embodiments of the disclosure, the temperature of the substrate during the deposition of the first group IVA semiconductor layer 304A may also be utilized during the treatment process, i.e., whilst contacting the exposed surface of the first group IVA semiconductor layer 204A with the first gas, in other words, the substrate temperature does not change from the first deposition process to the surface treatment process. In addition, the pressure in the reaction chamber may be maintained at a substantially constant value between the deposition of the first group IVA semiconductor layer 304A and the treatment processes for the exposed surface of the first group IVA semiconductor. In alternative embodiments of the disclosure, the temperature of the substrate and the pressure within the reaction chamber may be altered between the deposition of the first group IVA semiconductor layer 304A and during the treatment process. For example, the substrate temperature and the pressure within the reaction chamber may need to be adjusted in preparation for the subsequent layer to be deposited over the first group IVA semiconductor layer 304A. In some embodiments, the pressure in the reaction chamber whilst contacting the exposed surface of the first group IVA semiconductor layer to the first gas, i.e., the surface treatment process, may be less than 760 Torr, or less than 100 Torr, or even less than 10 Torr.

Once the exposed surface of the first group IVA semiconductor layer 304A has been contacted with the first gas for a desired period of time, the method 200 may continue with a process block 230 (FIG. 2) comprising, depositing a second group IVA semiconductor layer over a surface of the first group IVA semiconductor layer. In more detail, the semiconductor structure 305 (FIG. 3B) may be heated to a desired deposition temperature, i.e., a desired substrate temperature, within the reaction chamber of a chemical vapor deposition system. For example, the substrate may heated to a substrate temperature of less than approximately 700° C., or less than approximately 600° C., or less than approximately 550° C., or less than 500° C., or less than approximately 400° C., or even less than 300° C. In some embodiments of the disclosure, the temperature is maintained between the various process blocks of method 200, in other words, the deposition of the first group IVA semiconductor layer, the surface treatment of the exposed surface of the first group IVA semiconductor layer with the first gas, and the deposition of the second group IVA semiconductor layer, may all be performed at the same substrate temperature. In alternative embodiments, the temperature of substrate may be adjusted between the various process blocks, i.e., a different substrate temperature may be utilized for the deposition of the first group IVA semiconductor layer, the treatment process with the first gas, and the deposition of the second group IVA semiconductor layer.

In addition to controlling the substrate temperature during the deposition of the second group IVA semiconductor layer, it may also be desirable to also control the pressure within the reaction chamber to a desired set point. For example, the pressure within the reaction chamber during the deposition of the second group IVA semiconductor layer may be less than 760 Torr, or less than 100 Torr, or even less than 10 Torr. In some embodiments of the disclosure, the pressure within the reaction chamber is maintained at a substantially constant value during the method 200, i.e., the pressure within reaction chamber may be maintained a substantially constant value during the deposition of the first group IVA semiconductor, the surface treatment of the exposed surface of the first group IVA semiconductor layer with the first gas, and the deposition of the second group IVA semiconductor layer. In alternative embodiments the pressure within the reaction chamber may varied between the various process blocks of method 200, i.e., different reaction chamber pressures may be utilized for the deposition of the first group IVA semiconductor layer, the treatment process with the first gas, and the deposition of the second group IVA semiconductor layer.

In some embodiments of the disclosure, once the semiconductor structure 305 (FIG. 3B) has been heated to a desired deposition temperature and the reaction chamber pressure has been set, one or more precursor gases may be introduced into the reaction chamber and contact the exposed surface of the first group IVA semiconductor layer 304A, thereby depositing a second group IVA semiconductor layer 306A over the exposed surface of the underlying first group IVA semiconductor layer 304A (FIG. 3C) via a chemical vapor deposition process. In some embodiments, the second group IVA semiconductor layer 306A may comprise at least one of silicon (Si), germanium (Ge), silicon germanium (Si_(1-x)Ge_(x)), germanium tin (GeSn), silicon carbide (SiC), or silicon germanium tin (SiGeSn).

In a particular embodiment of the disclosure, the second group IVA semiconductor layer 306A may comprise a silicon (Si) layer. For example, the second group IVA semiconductor layer 306A may comprise a silicon (Si) layer and may be deposited by contacting the exposed surface of the first group IVA semiconductor layer with one or more silicon precursors, including, but not limited to, silane (SiH₄), disilane (Si₂H₆), trisilane (Si₃H₈), tetrasilane (Si₄H₁₀), isopentasilane (Si₅H₁₂), or neopentasilane (Si₅H₁₂). In some embodiments, the silicon precursor may comprise a higher order silane precursor with the general empirical formula Si_(x)H_((2x+2)). In some embodiments, the silicon precursor gas may comprise dichlorosilane (DCS). In some embodiments, the flow rate of the silicon precursor may be greater than 10 sccm, or greater than 50 sccm, or greater than 100 sccm, or ever greater than 200 sccm.

In some embodiment of the disclosure, the second group IVA semiconductor layer 306A may be deposited to a thickness of less than 500 nanometers, or less than 250 nanometers, or less than 100 nanometers, or less than 50 nanometers, or less than 25 nanometers, or less than 10 nanometers, or less than 5 nanometers, or even less than 1 nanometer.

The deposition of the second group IVA semiconductor layer 306A over a surface of the first group IVA semiconductor layer 304A may result in the formation of an interface layer 308A, the interface layer 308A being disposed between the second group IVA semiconductor 306A and the first group IVA semiconductor layer 304A, as illustrated by the semiconductor structure 310 of FIG. 3C.

In a particular embodiment of the disclosure, the first group IVA semiconductor layer 304A may comprise a silicon germanium (Si_(1-x)Ge_(x)) layer and the second group IVA semiconductor layer may comprise a silicon (Si) layer, and the interface layer 308A may be disposed between the two group IVA semiconductor layers. As a non-limiting example, the silicon germanium layer (Si_(1-x)Ge_(x)) 304A may comprise a germanium composition (x) of approximately 0.30, and a silicon (Si) layer 306A may be disposed over the silicon germanium (Si_(1-x)Ge_(x)) layer thereby forming the interface layer 308A therebetween. The thickness of the interface layer 308A may be determined by the thickness of the region between the two adjacent group IVA semiconductor layers in which the composition of the interface layer does not comprise either that of the underlying silicon germanium (Si_(0.70)Ge_(0.30)) layer 304A or that of overlying silicon (Si) layer 306A but rather the germanium composition (x) in the interface layer 308A, or interface region, may comprise a graded composition that varies in an approximate linear manner between a germanium composition (x) equal to approximately 0.30 in the silicon germanium (Si_(0.70)Ge_(0.30)) layer 304A to a germanium composition (x) equal to approximately 0.00 in the silicon (Si) layer 306A.

In some embodiments of the disclosure, the interface layer 308A thickness may be determined utilizing one or more of spectroscopic ellipsometry (SE), secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), or x-ray reflectometry (XRR). In a particular embodiment, the interface layer 308A thickness may be determined by spectroscopic ellipsometry (SE) and utilizing such an analytic technique may determine an interface layer 308A thickness of less than approximately 30 Angstroms, or less than approximately 20 Angstroms, or even less than approximately 15 Angstroms. It should be noted that the interface layer thicknesses disclosed herein, e.g., less than approximately 15 Angstroms, may be achieved utilizing a deposition process and particularly may be achieved utilizing a chemical vapor deposition (CVD) process, wherein CVD processes are distinct from alternative deposition methods, such as, for example, molecular beam epitaxy (MBE), or atomic layer deposition (ALD).

As a non-limiting example of the embodiments of the disclosure, FIG. 4 illustrates a cross sectional transmission electron microscopy (TEM) image of a semiconductor structure 400 deposited according to the embodiments of the disclosure. The semiconductor structure 400 includes a silicon (Si) layer 402, a silicon germanium (Si_(0.70)Ge_(0.30)) layer 404 disposed over the silicon (Si) layer 402, and an additional silicon (Si) layer 406 disposed over the silicon germanium (Si_(0.70)Ge_(0.30)) layer 404, thereby forming a Si/(Si_(0.70)Ge_(0.30))/Si semiconductor stack structure. The semiconductor structure 400 was deposited at a substrate temperature of 500° C. utilizing disilane (Si₂H₆) as the silicon precursor and germane (GeH₄) as the germanium precursor. In addition, the upper exposed surface of the silicon germanium (Si_(0.70)Ge_(0.30)) layer 404 was contacted with a first gas comprising hydrochloride acid and dichlorosilane prior to the deposition of the overlying silicon (Si) layer 406.

The semiconductor structure 400 also includes two interface layers 408 and 410, wherein interface layer 408 is disposed between the silicon (Si) layer 402 and the silicon germanium (Si_(0.70)Ge_(0.30)) layer 404, and wherein interface layer 410 is disposed between the silicon germanium (Si_(0.70)Ge_(0.30)) layer 404 and the additional silicon (Si) layer 406. Examination of the TEM image of FIG. 4 demonstrates that the both the interface layers 408 and particular the interface layer 410 are abrupt, thin interfaces without a “blurry” boundary between the two adjacent group IVA semiconductor layers.

Upon depositing the second group IVA semiconductor layer 306A (FIG. 3C) to a desired thickness, the method 200 may proceed with an optional process block 240 comprising, contacting an exposed surface of the second group IVA semiconductor with a second gas. In some embodiments, the second gas may comprise a second chloride gas. For example, in some embodiments the second chloride gas may comprise at least one of hydrochloric acid (HCl), or chlorine (Cl₂). In addition, in some embodiments the second gas may further comprise a second group IVA gas, such as, for example, at least one of dichlorosilane (DCS), dichlorodisilane, trichlorosilane, tetrachlorosilane, hexachlorosilane, silane, or germane. In some embodiments of the disclosure, the second gas may contact the exposed surface of the second group IVA semiconductor layer for a time period of less than 60 seconds, or less than 30 seconds, or even less than 10 seconds.

In some embodiments of the disclosure, the method 200 comprising, depositing a first group IVA semiconductor layer (process block 210), contacting an exposed surface of the first group IVA semiconductor layer with a first gas (process block 220), depositing a second group IVA semiconductor layer (process block 230), and optionally contacting an exposed surface of the second group IVA semiconductor with a second gas (process block 240), may collectively comprise a deposition cycle and the method may further comprise repeating the deposition cycle one or more times.

In more detail, a deposition cycle may be utilized to deposit a bilayer semiconductor structure 312A (FIG. 3C) comprising a first group IVA semiconductor layer 304A and a second group IVA semiconductor layer 306A, with an interface layer 308A disposed therebetween, the interface layer 308A having a minimized thickness due to the embodiments of the disclosure. Therefore, the method 200 (FIG. 2) may further comprise a decision gate 250 which determines if the deposition is cycle is repeated, the decision gate 250 being dependent on the desired thickness of the overall semiconductor structure (i.e., the number of bilayer semiconductor structures). If a greater thickness, i.e., a greater number of bilayer semiconductor structures, is required then the method 200 repeats via process the block 260, which returns the method 200 to the process block 210 and deposits an additional bilayer semiconductor structure. Alternatively, if the desired thickness is achieved, i.e., the desired number of bilayer semiconductor structures, then the process may terminate at a process block 270 and the semiconductor stack structure deposited may be subjected to further fabrication processes to produce a semiconductor device structure.

FIG. 3D illustrates a semiconductor structure 314 which comprises the semiconductor structure 310 (FIG. 3C) after having performed an additional deposition cycle of method 200. The additional deposition cycle therefore deposits an additional bilayer semiconductor structure 312B comprising an additional first group IVA semiconductor layer 304B and an additional second group IVA semiconductor layer 306B. Disposed between the additional first group IVA semiconductor layer 304B and the additional second group IVA semiconductor layer 306B is an additional interface layer 308B, wherein the additional interface layer 308B has an interface layer thickness of less than 30 Angstroms, or less than 20 Angstroms, or even less than 15 Angstroms. In a particular embodiment of the disclosure, the additional first group IVA semiconductor layer 304B may comprise a silicon germanium (Si_(1-x)Ge_(x)) layer (e.g., (x)=0.30) and the additional second group IVA semiconductor layer 306B may comprise a silicon (Si) layer.

FIG. 3E illustrates a semiconductor structure 316 which comprises the semiconductor structure 314 (FIG. 3D) after having performed a further deposition cycle of method 200. The further deposition cycle therefore deposits a further bilayer semiconductor structure 312C comprising, a further first group IVA semiconductor layer 304C and a further second group IVA semiconductor layer 306C. Disposed between the further first group IVA semiconductor layer 304C and the further second group IVA semiconductor layer 306C is a further interface layer 308C, wherein the further interface layer 308C has an interface layer thickness of less than 30 Angstroms, or less than 20 Angstroms, or even less than 15 Angstroms. In a particular embodiment of the disclosure, the further first group IVA semiconductor layer 304C may comprise a silicon germanium (Si_(1-x)Ge_(x)) layer, e.g., (x)=0.30, and the further second group IVA semiconductor layer 306C may comprise a silicon (Si) layer.

It should be noted that in some embodiments of the disclosure, the deposition cycle of method 200 (FIG. 2) may be halted after the deposition of a first group IVA semiconductor layer such that rather than a bilayer semiconductor structure being deposited instead a single group IVA semiconductor layer may be deposited. For example, a number of bilayer semiconductor structures may be deposited according to the embodiments of the disclosure and the multiple bilayer structures may be covered, or at least partially covered, by the deposition of a single group IVA semiconductor layer.

The embodiments of the disclosure may also include a number of semiconductor structures deposited according to the methods described herein. In some embodiments of the disclosure, a semiconductor structure 316 (FIG. 3E) may comprise a silicon substrate 302, a first silicon germanium (Si_(1-x)Ge_(x)) layer 304A disposed over a surface of the silicon substrate, and a first silicon (Si) layer 306A disposed over the first silicon germanium (Si_(1-x)Ge_(x)) layer 304A. In some embodiments, the semiconductor structure 316 may also comprise, a first interface layer 308A disposed between the first silicon germanium (Si_(1-x)Ge_(x)) layer 304A and the first silicon (Si) layer 306A, wherein the interface layer has a thickness of less than 15 Angstroms.

In some embodiments of the disclosure, the semiconductor structure 316 may further comprise, a second silicon germanium (Si_(1-x)Ge_(x)) layer 304B disposed over the first silicon layer 306A, and a second silicon layer 306B disposed over the second silicon germanium (Si_(1-x)Ge_(x)) layer 304B. The semiconductor structure 316 may further comprise, a second interface layer 308B disposed directly between the second silicon germanium (Si_(1-x)Ge_(x)) layer 304B and the second silicon layer 306B, wherein the second interface layer 308B has a thickness of less than 15 Angstroms.

In some embodiments of the disclosure, the semiconductor structure 316 may further comprise, a third silicon germanium (Si_(1-x)Ge_(x)) layer 304C disposed over the second silicon layer 306B, and a third silicon layer 306C disposed over the third silicon germanium (Si_(1-x)Ge_(x)) layer 304C. The semiconductor structure 316 may also comprise, a third interface layer 308C disposed directly between the third silicon germanium (Si_(1-x)Ge_(x)) layer 304C and the third silicon layer 306C, wherein the third interface layer 308C has a thickness of less than 15 Angstroms.

The example embodiments of the disclosure described above do not limit the scope of the invention, since these embodiments are merely examples of the embodiments of the invention, which is defined by the appended claims and their legal equivalents. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the disclosure, in addition to those shown and described herein, such as alternative useful combination of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims. 

What is claimed is:
 1. A method for depositing a semiconductor structure on a surface of a substrate, the method comprising: depositing a first group IVA semiconductor layer, comprising silicon germanium (Si_(1-x)Ge_(x)), over a surface of the substrate; contacting an exposed surface of the first group IVA semiconductor layer with a first gas comprising a first chloride gas; depositing a second group IVA semiconductor layer, comprising silicon, over a surface of the first group IVA semiconductor layer; and forming an interface region between the first group IVA semiconductor layer and the second group IVA semiconductor layer, wherein the interface region comprises a graded composition between having silicon germanium (Si_(1-x)Ge_(x)) wherein x equals 0.3 proximate the first group IVA semiconductor layer and having silicon germanium (Si_(1-x)Ge_(x)) wherein x equals 0 proximate the second group IVA semiconductor layer.
 2. The method of claim 1, wherein the first gas further comprises a first group IVA gas.
 3. The method of claim 2, wherein the first group IVA gas comprises at least one of dichlorosilane (DCS), dichlorosilane, trichlorosilane, tetrachlorosilane, hexachlorosilane, silane, or germane.
 4. The method of claim 2, wherein the flow rate ratio of the first chloride gas in relation to the first group IVA gas is less than 2:1.
 5. The method of claim 2, wherein the contacting the exposed surface of the first group IVA semiconductor layer with the first gas results in substantially no net deposition of material.
 6. The method of claim 1, wherein the surface of the substrate comprises a silicon surface.
 7. The method of claim 1, wherein the first group IVA semiconductor layer has a germanium composition (x) equal to or greater than 0.30.
 8. The method of claim 1, wherein the first chloride gas comprises at least one of hydrochloric acid (HCl), or chlorine (Cl₂).
 9. The method of claim 1, wherein contacting an exposed surface of the first group IVA semiconductor layer with the first gas further comprises, contacting the exposed surface for a time period of less than 60 seconds.
 10. The method of claim 1, further comprising contacting an exposed surface of the second group IVA semiconductor layer with a second gas comprising a second chloride gas.
 11. The method of claim 10, wherein the second gas further comprises a second group IVA gas.
 12. The method of claim 1, wherein a thickness of the interface region is less than 30 Angstroms.
 13. The method of claim 12, wherein the thickness of the interface region is less than 15 Angstroms.
 14. The method of claim 1, wherein a deposition cycle of the method comprises the depositing the first group IVA semiconductor layer, the contacting the exposed surface of the first group IVA semiconductor layer with the first gas, and the depositing the second group IVA semiconductor layer, and wherein the method further comprises repeating the deposition cycle one or more times.
 15. The method of claim 14, further comprising forming a plurality of interface regions, each of the interface regions having a thickness of less than 15 Angstroms.
 16. The method of claim 1, further comprising heating the substrate to a substrate temperature of less than 700° C.
 17. A semiconductor structure deposited according to the method of claim
 1. 18. A semiconductor structure comprising: a silicon substrate; a first silicon germanium (Si_(1-x)Ge_(x)) layer disposed over a surface of the silicon substrate; a first silicon layer disposed over the first silicon germanium (Si_(1-x)Ge_(x)) layer; and a first interface region disposed directly between the first silicon germanium (Si_(1-x)Ge_(x)) layer and the first silicon layer, wherein the interface region comprises a graded composition between having silicon germanium (Si_(1-x)Ge_(x)) wherein x equals 0.3 proximate the first silicon germanium (Si_(1-x)Ge_(x)) layer and having silicon germanium (Si_(1-x)Ge_(x)) wherein x equals 0 proximate the first silicon layer.
 19. The semiconductor structure of claim 18, further comprising: a second silicon germanium (Si_(1-x)Ge_(x)) layer disposed over the first silicon layer; a second silicon layer disposed over the second silicon germanium (Si_(1-x)Ge_(x)) layer; and a second interface region disposed directly between the second silicon germanium (Si_(1-x)Ge_(x)) layer and the second silicon layer; wherein the second interface region has a thickness of less than 15 Angstroms.
 20. The semiconductor structure of claim 19, further comprising: a third silicon germanium (Si_(1-x)Ge_(x)) layer disposed over the second silicon layer; a third silicon layer disposed over the third silicon germanium (Si_(1-x)Ge_(x)) layer; and a third interface layer region disposed directly between the third silicon germanium (Si_(1-x)Ge_(x)) layer and the third silicon layer; wherein the third interface region has a thickness of less than 15 Angstroms. 